The information described in this background section is not admitted to be prior art.
Extracorporeal membrane oxygenation (ECMO), also referred to as extracorporeal life support (ECLS), is a clinical life support technique that bypasses the arteriovenous circuit and provides external blood oxygenation to patients suffering from cardiac and/or respiratory failure. For example, ECMO may be used in patients with severe acute respiratory distress syndrome (ARDS) or chronic obstructive pulmonary disease (COPD) as a bridge treatment to lung transplantation. Many patients on ECMO are relatively debilitated and therefore do not possess appreciable ambulatory mobility, which may lead to muscular atrophy and contribute to increased post-transplant morbidity and mortality. As a result, physicians increasingly support the idea that improving a patient's functional status (e.g., their ambulatory mobility) pre-transplant, and while on ECMO, may decrease post-transplant morbidity and mortality. However, pre-transplant rehabilitation of ECMO patients—for example, by walking, i.e., ambulatory ECMO—is difficult to implement in practice because of the size and mass of ECMO equipment (e.g., the blood pump, tubing, oxygenator, heat exchanger, and venous reservoir) and the instability of the ECMO cannulation site.
There are two general types of ECMO techniques: veno-arterial (VA ECMO) and veno-venous (VV ECMO). In VA ECMO, a first cannula is surgically or percutaneously inserted through a patient's right jugular vein, right brachiocephalic vein, and superior vena cava, and into their right atrium, and a second cannula is surgically or percutaneously inserted through the patient's right carotid artery and right brachiocephalic artery, and into their aortic arch. In VV ECMO, a double-lumen cannula is surgically or percutaneously inserted through a patient's right jugular vein, right brachiocephalic vein, and superior vena cava, and into their right atrium and inferior vena cava. VV ECMO can also be performed with two separate cannula, for example, a first cannula inserted through a patient's right jugular vein, and a second cannula inserted through a different vein such as the femoral vein. VA ECMO and VV ECMO can also be performed with peripheral cannulation through a patient's femoral vein and femoral artery, or through an axillary approach to the subclavian artery, such as, for example, in the patient's armpit, but peripheral techniques are less common.
In central VA ECMO, deoxygenated blood is withdrawn through the atrial cannula, pumped through an oxygenator and heat exchanger, and the re-oxygenated blood is returned to the patient through the aortic cannula. In VV ECMO, deoxygenated blood is withdrawn from the inferior vena cava and superior vena cava through distal and proximal drainage ports in the dual lumen cannula, pumped through an oxygenator and heat exchanger, and the re-oxygenated blood is returned to the patient through an intermediate infusion port in the dual lumen cannula, which is positioned in the right atrium to direct the re-oxygenated blood flow across the patient's tricuspid valve and into their right ventricle.
The positioning of the cannula in ECMO patients is critical to the success of the technique. Therefore, stabilizing and maintaining the position of the cannula, and the tubing connecting the cannula to the external ECMO circuit, are essential. For example, it is important to not subject the cannula and its insertion site to movements and associated stresses that approach, let alone exceed, the limits of the sutures that hold the cannula in place, which places strict limits on a patient's head and neck movements. The strict limits on ECMO patients' head and neck movements, due to the instability of the cannulation site, make walking while on ECMO (ambulatory ECMO) difficult to perform.